Enhanced Oil Recovery (EOR) may be used to increase oil recovery in fields worldwide. There are three main types of EOR, thermal, chemical/polymer and gas injection, which may be used to increase oil recovery from a reservoir, beyond what can be achieved by conventional means—possibly extending the life of a field and boosting the oil recovery factor.
Thermal enhanced recovery works by adding heat to the reservoir. The most widely practiced form is a steamdrive, which reduces oil viscosity so that it can flow to the producing wells. Chemical flooding increases recovery by reducing the capillary forces that trap residual oil. Polymer flooding improves the sweep efficiency of injected water. Miscible injection works in a similar way to chemical flooding. By injecting a fluid that is miscible with the oil, trapped residual oil can be recovered.
Referring to FIG. 1, there is illustrated prior art system 100. System 100 includes underground formation 102, underground formation 104, underground formation 106, and underground formation 108. Production facility 110 is provided at the surface. Well 112 traverses formations 102 and 104, and terminates in formation 106. The portion of formation 106 is shown at 114. Oil and gas are produced from formation 106 through well 112, to production facility 110. Gas and liquid are separated from each other, gas is stored in gas storage 116 and liquid is stored in liquid storage 118.
U.S. Pat. No. 5,826,656 discloses a method for recovering waterflood residual oil from a waterflooded oil-bearing subterranean formation penetrated from an earth surface by at least one well by injecting an oil miscible solvent into a waterflood residual oil-bearing lower portion of the oil-bearing subterranean formation through a well completed for injection of the oil miscible solvent into the lower portion of the oil-bearing formation; continuing the injection of the oil miscible solvent into the lower portion of the oil-bearing formation for a period of time equal to at least one week; recompleting the well for production of quantities of the oil miscible solvent and quantities of waterflood residual oil from an upper portion of the oil-bearing formation; and producing quantities of the oil miscible solvent and waterflood residual oil from the upper portion of the oil-bearing formation. The formation may have previously been both waterflooded and oil miscible solvent flooded. The solvent may be injected through a horizontal well and solvent and oil may be recovered through a plurality of wells completed to produce oil and solvent from the upper portion of the oil-bearing formation. U.S. Pat. No. 5,826,656 is herein incorporated by reference in its entirety.
Co-pending U.S. patent application Ser. No. 11/409,436, having Publication Number 2006/0254769, published Nov. 16, 2006, issued as U.S. Pat. No. 7,426,959, discloses a system including a mechanism for recovering oil and/or gas from an underground formation, the oil and/or gas comprising one or more sulfur compounds; a mechanism for converting at least a portion of the sulfur compounds from the recovered oil and/or gas into a carbon disulfide formulation; and a mechanism for releasing at least a portion of the carbon disulfide formulation into a formation. U.S. Patent Application Publication Number 2006/0254769 is herein incorporated by reference in its entirety.
U.S. Pat. No. 5,062,970 discloses a surfactant composition, suitable for enhanced oil recovery comprising in a 60:40 to 10/90 weight ratio a) (o,m)- and/or (o,p)-dialkylbenzene alkali sulfonate and b) polyalkoxyphenyl ether alkali sulfonate. U.S. Pat. No. 5,062,970 is herein incorporated by reference in its entirety.
Other compositions and methods for enhanced hydrocarbons recovery are described in U.S. Pat. No. 3,943,160; U.S. Pat. No. 3,946,812; U.S. Pat. No. 4,077,471; U.S. Pat. No. 4,216,079; U.S. Pat. No. 5,318,709; U.S. Pat. No. 5,723,423; U.S. Pat. No. 6,022,834; U.S. Pat. No. 6,269,881; and by Wellington, et al. in “Low Surfactant Concentration Enhanced Waterflooding,” Society of Petroleum Engineers, 1995; all of which are incorporated by reference herein.
There is a need in the art for improved systems and methods for enhanced oil recovery. There is a further need in the art for improved systems and methods for enhanced oil recovery using a solvent, for example through viscosity reduction, chemical effects, and miscible flooding. There is a further need in the art for improved systems and methods for solvent miscible flooding. There is a further need in the art for improved systems and methods for recovering a solvent after miscible flooding.